With the market requirements for brightness, color saturation, service life, non-toxic environmental protection, etc of projection apparatus, the types of light sources used in the projection apparatus have evolved from UHP lamp, light emitting diode (LED) to laser diode (LD).
At present, the cost of high-brightness red laser diodes and green laser diodes is too high. In order to reduce the cost, a blue laser diode is used to excite the phosphor powder on the phosphor wheel to generate yellow light and green light. The desired red light is filtered out of the yellow light by a filter wheel. Together with the blue light emitted by the blue laser diode, the three primary colors of red, green and blue required for the projection image are generated.
Currently, the phosphor wheel is an extremely important optical component of the projection apparatus using a laser diode as a light source. However, conventional aluminum substrates are easily deformed at a high temperature due to their low temperature resistance. Therefore, the wavelength-converting layer and the diffusion reflection layer are required to be cured at a high temperature, and then are demolded and attached onto the aluminum substrate. A plurality of pores is generated in the process, which affects the conversion efficiency and reflectivity of the phosphor wheel.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.